The subject matter described herein relates generally to methods and systems for the maintenance of wind turbines, and more particularly, to methods and systems for avoiding sounds from loose particles moving around freely in the interior of wind turbine rotor blades.
At least some known wind turbines include a tower and a nacelle mounted on the tower. A rotor is rotatably mounted to the nacelle and is coupled to a generator by a shaft. A plurality of blades extend from the rotor. The blades are oriented such that wind passing over the blades turns the rotor and rotates the shaft, thereby driving the generator to generate electricity.
The blades are generally hollow, their bodies include laminates including glass fibre and resin. Typically, two halves are laminated together during the manufacturing process of a rotor blade. After the rotor blade is produced by joining the two halves, on the inside of the blade some fibers of the laminate may stick out of the inner surface or the like. During subsequent operation of the wind turbine, as the blade is subject to changing loads resulting in slight deformation of its body, fibers and particles may become loose. As a result, after some time a number of loose particles may build up in the interior of the blade. These particles have typical sizes from about 0.2 cm to 4 cm.
This is undesirable, as they move around during operation of the turbine, or even during idle operation of the turbine, when the blades are in a feathered position. This may lead to damage if e.g., bigger pieces hit a sensor inside the rotor blade. A further disadvantage is that once a certain number of particles are moving inside the blade, the sound of the particles sliding along the interior of the blade is audible outside the turbine as a kind of noise. Though this is only audible during idle or standstill of the turbine, as during operation there are many louder sound sources, it is still not desirable. For instance, persons not informed about the cause of the sound may tend to think that there is a malfunction in the turbine.
In view of the above, it is desirable to have a method and system for avoiding the sounds caused by loose particles inside rotor blades.